audit: type=1800 audit(1589900450.937:9): pid=6441 uid=0 auid=0 ses=5 subj=system_u:system_r:kernel_t:s0 op=collect_data cause=failed(directio) comm="syz-executor456" name="file0" dev="sda1" ino=15705 res=0
MINIX-fs: mounting unchecked file system, running fsck is recommended
Process accounting resumed
==================================================================
BUG: KASAN: use-after-free in add_chain fs/minix/itree_common.c:14 [inline]
BUG: KASAN: use-after-free in get_branch fs/minix/itree_common.c:52 [inline]
BUG: KASAN: use-after-free in get_block+0x1047/0x1300 fs/minix/itree_common.c:160
Read of size 2 at addr ffff888088dde644 by task syz-executor456/6441

CPU: 1 PID: 6441 Comm: syz-executor456 Not tainted 4.19.123-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
 add_chain fs/minix/itree_common.c:14 [inline]
 get_branch fs/minix/itree_common.c:52 [inline]
 get_block+0x1047/0x1300 fs/minix/itree_common.c:160
 minix_get_block+0xe5/0x110 fs/minix/inode.c:379
 __block_write_begin_int+0x480/0x17a0 fs/buffer.c:1978
 __block_write_begin fs/buffer.c:2028 [inline]
 block_write_begin+0x58/0x2e0 fs/buffer.c:2087
 minix_write_begin+0x35/0xe0 fs/minix/inode.c:415
 generic_perform_write+0x1f8/0x4d0 mm/filemap.c:3162
 __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3287
 generic_file_write_iter+0x37f/0x729 mm/filemap.c:3315
 call_write_iter include/linux/fs.h:1821 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x512/0x760 fs/read_write.c:487
 __kernel_write+0x109/0x370 fs/read_write.c:506
 do_acct_process+0xcd8/0x10e0 kernel/acct.c:520
 slow_acct_process kernel/acct.c:579 [inline]
 acct_process+0x517/0x5c0 kernel/acct.c:605
 do_exit+0x1738/0x2f30 kernel/exit.c:870
 do_group_exit+0x125/0x350 kernel/exit.c:983
 __do_sys_exit_group kernel/exit.c:994 [inline]
 __se_sys_exit_group kernel/exit.c:992 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:992
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4445d8
Code: Bad RIP value.
RSP: 002b:00007ffe9d220398 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00000000004445d8
RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
RBP: 00000000004c70d0 R08: 00000000000000e7 R09: ffffffffffffffd4
R10: 00007ffe9d2202b0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d95e0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0002237780 count:0 mapcount:-128 mapping:0000000000000000 index:0x1
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea0002133c88 ffffea0002130ac8 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888088dde500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888088dde580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888088dde600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888088dde680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888088dde700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================